In the area of visual/optical surveillance, one of the primary objectives is to efficiently scan a wide area of coverage, with sufficiently high resolution to enable detection, recognition, and identification of objects from airborne and/or elevated surveillance platforms. Prior attempts to address this issue focused on solutions such as continuous scan TDI (Time Delay & Integration) systems, large, monolithic focal plane arrays (FPAs), and two-axis scan mirrors to allow for a greater range of view.
Continuous scan TDI systems cannot cover a large area with good resolution and/or ground sample distance (GSD) and quick revisit rates. Large, monolithic FPAs or buttable FPAs are expensive and difficult to produce in sufficient size/quantity and have limited ground coverage areas. Two-axis scan mirrors are slow, expensive, and prone to failure and/or alignment problems.